Paint, stain and the like are conventionally sold at the retail level in metal pails of a one gallon size having an upper edge with a groove in which an annular edge of a metal cover is secured by a press fit. Opening of the cover is performed by prying the cover edge upwardly in order to open the pail so that the stored paint or stain can be used. Such metal pails are conventionally made from tin plated steel which has become more and more expensive in the recent past. Also, the ever-increasing use of water-based latex paint with steel paint pails has necessitated the use of a special coating on the interior of the pail in order to prevent the water from causing corrosion as the paint is stored. Another problem with metal paint pails is that such pails tend to dent when struck or dropped.
One prior attempt at making a paint pail from other than metal utilized injection/blow molding of polypropylene plastic in order to overcome the corrosion problem when water-based latex paints are stored. This pail required a molded bead on the inner surface at the upper end of the pail in order to secure an associated cover with the required strength that is necessary to pass drop tests that paint pails are subjected to before being accepted commercially by paint manufacturers.
In securing the cover in position, it is also important that the cover be easily removable when desired so that the paint can be used. One might think that helical threads on a plastic paint pail would advantageously permit secure closing of the cover as well as easy opening. However, such a plastic pail and cover construction would not be commercially acceptable as paint manufacturers have extensive capital investments in dispensing machinery that is only capable of closing the cover by a unidirectional movement such as is used with the conventional metal pail and cover fit that is pried open.
U.S. Pat. Nos. relating to containers, retainers and the like include: 680,386; 1,596,367; 1,672,839; 2,069,125; 2,148,468; 2,205,685; 2,257,715; 2,304,912; 2,467,392; 2,487,400; 2,542,350; 2,556,765; 2,971,671; 3,288,342; 3,329,302; 3,355,060; 3,380,610; 3,433,385; 3,804,288; 3,814,277; 3,815,777; 3,868,041; 3,878,963; 3,931,891; and 4,053,078.